The present invention relates to a light distribution device and more particularly to a device which is able to receive the light transmitted through a single light-guide cable and able to time-sharingly distribute the same to a large number of light-guide cables each in turn. More concretely, the present invention relates to a device which is capable of effectively supplying light necessary for the photosynthesis of objects such as algae (as for example, chlorella, spirulina etc.), photosynthetic bacteria and other artificially photosynthesized substances (as for instance, callus and the like) or plants, mushrooms etc.
A chlorella culturing device, as an example of a photosynthetic reactor, has been proposed, in which chlorella is cultured by using light and carbon dioxide to effect photosynthesis. However, as a result of detailed research into the photosynthetic process it has been found that one cycle of photosynthetic reaction in chlorella requires only brief light radiation (of about 10 micro-seconds) and in the remaining time (of about 200 micro-seconds) the photosynthetic reaction can be conducted without light radiation, more explicitly, the cycle of reaction can be more effectively performed with no light radiation for the remaining duration of the cycle. On the other hand, in case of chlorella culturing it is usual to use such a photosynthetic reactor (for instance, a chlorella culturing bath) wherein a large number of fluorescent lamps are arranged so as to allow the photosynthetic substances to pass through the gaps between the lamps. Said conventional bath, due to the use of a large number of fluorescent lamps, is large in size and consumes a large amount of electric energy. Furthermore it necessitates hard treatment of heat generated by the lamps. To solve these problems, the present applicant has previously proposed that solar rays or artificial rays be focused and introduced into a fiber optic cable and then transmitted therethrough to a light radiator which is used as a light source for a photosynthetic reactor. However, it is also evident that when a large scale photosynthetic reactor is constructed with the use of the above-mentioned light-radiating means, a large number of light radiators must be used or a large-sized device for focusing the sun's rays and/or artificial light rays is necessary.
To solve the above-mentioned problems, the present applicant has also proposed a light distribution device which is able to intermittently supply light energy to photosynthetic substances in order to more effectively promote the process of photosynthesis and therefore is sufficient to cover the need for light energy for any large-scale photosynthetic reactor at the fixed capacity of a solar ray and/or artificial light ray focusing device.
The present applicant has previously proposed a photosynthetic reactor's light source having a light-guiding rod or a light-guide cable for transmitting solar rays or artificial light rays focused by lenses and a transparent rotary rod. The light-emitting end of the light guide is disposed opposite to the rotating axis of the revolving rod, and a reflecting mirror is provided at the rotating axis of the revolving rod against the light-emitting end of the light guide. The light transmitted through the light guide and introduced into the revolving rod is reflected by said mirror and propagates toward the tip portion of the revolving rod, where the light is reflected again by a mirror provided thereat and then radiated out from the light-emitting surface of the revolving rod. A large number of light-guide cables are arranged to form a ring in opposition to the light-emitting surface of the revolving rod. Consequently, when the revolving rod is driven by a motor, the light-receiving faces of the light-guide cables, to be covered with the light-emitting surface of the revolving rod, are changed in turn and each light-guide cables receives instant light radiation for one cycle of rotation of the rotary rode. The end portion of each light-guide cables serves as a light radiator. The light radiators may be provided at a certain distance from each other in a photosynthetic reactor or widely spread apart in a plant cultivating room, a mushroom cultivating place etc.
As described above, in the case of the above-mentioned light distribution device, the light delivered thereto through the light guide can be supplied momentarily into the light guide cables each in turn through the revolving rod and, accordingly, the distributed light can be discharged momentarily from the output end of each light-guide cable at every rotation of the rotary rod into a photosynthetic reactor wherein a photosynthetic substance is radiated with light rays for a very short period, for instance, about 10 micro-seconds that initiates a cycle of photosynthetic reaction and completes the cycle without any additional light radiation and at the next time of light radiation after one rotation of the revolving rod, it initiates a new cycle of photosynthetic reaction. A series of photosynthetic reactions in the reactor is thus continued with the periodical light radiation of the photosynthetic substances. For initiating the process of photosynthesis in the object it is necessary to supply no less than a specified amount of light energy. In the above-mentioned light distribution device a necessary amount of light energy may be easily obtained by increasing the density of the light by a very small amount corresponding to the light-emitting surface of the revolving rod. Thanks to this construction feature, the device can work with a compact solar ray or artificial light ray collecting device for introducing light rays into the light guide. Furthermore, since the light discharged from the light-emitting surface of the revolving rod is time-sharingly distributed to many light-guide cables, the device can supply enough light energy into a photosynthetic reactor of a large capacity.
However, the above-mentioned light distribution device has such drawbacks that the revolving rod is difficult to make and is expensive. In view of these drawbacks, the present applicant has proposed a further improved device capable of distributing light rays transmitted through a single light-guide cable among a large number of light-guiding cables by applying simpler and less expensive means.
The improved light distribution device previously proposed by the present applicant includes a primary single light-guide cable for transmitting solar rays or artificial light rays introduced into its light-receiving end and a large number of secondary light-guide cables, the light-receiving ends of which are arranged together to form a ring of a light-receiving plane. An arm to be rotated by a motor has at its front end a light coupler integrally secured thereto and also an auxiliary arm integrally secured thereto for holding the light-emitting end of the primary light-guide cable by loosely fitting said cable's end in a bearing provided at said auxiliary arm. An arm supports the end portion of the light-guide cable by loosely inserting said cable's end through a spherical bearing provided in its front end, preferably being aligned with the axis of the driving motor. Accordingly, when the motor rotates, the arm is rotated to move the light coupler with the light-emitting end of the light-guide cable along the ring-plane formed by the light-emitting ends of a large number of light-guide cables and, thereby, to realize the sequential distribution of the light to the light-guide cables in the same way as the aforesaid device. In this improved device, the light-guide cable can be rotated as being supported in the spherical bearing that eliminates the possibility of damaging said cable due to excessive friction. While in this case the spherical bearing supports the rotating axis of the guide cable, it is also possible to support the cable only in a loose hole of the arm without using a spherical bearing. However, in such a case there may be fear of damaging the outer surface of the cable due to the possible rubbing of said surface against the inner surface of the through-hole. In the same manner, the light-emitting end of the light-guide cable can be loosely fitted into the through-hole of the auxiliary arm without using a supporting bearing. In both cases the light-emitting end of the light-guide cable can be rotated without being twisted along the ring-plane formed by the light-emitting faces of a large number of light-guide cables.
However, in the above-mentioned light distribution device no limitation is placed on the use of the light-guide cables and nothing is proposed concerning their effective use that may fail in the effective utilization of the device. In particular, since each of the secondary light-guide cables receives only momentary light radiation for one revolution of the light-emitting end of the primary light-guide cable around the light-receiving ring, it must wait for the next light supply for a long time. Effective use of the light energy may not be assured due to the extended period of darkness as opposed to the light radiation period. It was also impractical to shorten the dark reaction period by increasing the revolution speed of the device because of the difficulty in maintaining the mechanical durability of the device against the increased centrifugal force.